Multiple local circuit for telegraphs



(No Model.)

F. L. POPE.

MULTIPLE LOCAL GIRGUIT FOR TELBGRAPHS. No.- 329,410.

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UNITED STATES PATENT @rrrca FRANK L. POPE, OF ELIZABETH, NEW JERSEY.

MULTIPLE LOCAL CIRCUIT FOR TELEGRAPHS.

SPECIFICATION forming part of Letters Patent No, 329,410, dated October 27, 1885.

Application filed March 11, 1885. Serial No. 158,420.

To all whom it may concern.-

Be it known that I, FRANK L. Porn, a citizen of the United States, residing at Elizabeth, in the county of Union and State of New Jersey, have invented certain new and useful Improvements in Multiple Local Circuits for Electric Telegraphy, of which the following is a specification.

In making use of the dynamo-electric machine for the purpose of supplying electric currents for large telegraph-stations the employment of such machines for supplying the local circuits (which, as is well known, consume by far the larger portion of the total electric energy required at any one station) has heretofore been attended with much practical difficulty. The volume or strength of electric current required in each local circuit is many times greater than that required in any of the main or long line circuits. Each individual local circuit is required to be alternately opened and closed by the action of its own relay without appreciably affecting the strength of current in any of the others, and this can only be effectually done by maintaining a constant difference of potential between the terminals of all the local circuits, irrespective of the number of them which may be open or closed at any particular time-that is to say, the potential of the current from the dynamoelectric machine must be maintained constant, although its volume or quantity is subject to great variation. This result has heretofore been attempted by the use of apair of dynamoelectric machines, the armature of the first machine being employed to supply an electric current to a number of local circuits placed in parallel or multiple arc, while the armature of the second machine is included in a sepa rate circuit, both with its own field-magnet and with the field-magnet of the first dynamo.

My invention consists in combining the 10- cal circuits of a large telegraph-station with the armature and field coils of a single dynamo-electric machine in such a manner that the supply of current to the several local circuits is rendered automatic or self-regulating, while at the same time a constant potential is maintained at the terminals of all the local circuits.

The accompanying drawing is a diagram (No model.)

representing my invention and illustrating the principle of distribution of electric current.

In the drawing, A represents the armature and armature-coil of a dynamo-electric machine, of which the terminals are shown at p n. F F arethe field-coils, which are of much greater length and consequently higher resistance than the coils of the armature, and which have their terminals united at p and a to those of the armature. The arrangement preferred in practice is that known as the shunt-dynamo. To the terminals 1) a are also respectively connected the leads P and N, by which the working current is conveyed to the local circuitsl Z, Ste. These local circuits are connected in parallel or multiple are between the leads P N. Each local curcuit includes the coils of a sounder or other telegraphic receiving-instrument, S, and is provided with a relay, It, the latter consisting of a circuitbreaker, k, which is caused to alternately make and break said local circuit in a well-known manner by the action of an electro-magnet, m, and an antagonistic spring, it. Each of the relay electromagnets m m is included in the circuit of a different telegraph-line, and opens and closes its corresponding local circuit independently of the others. It is apparent, therefore, that the leads P and N are united through the medium of a great number of local circuits, each of which is provided with an independently actuated circuit-breaker; hence the number of these circuits that are closed must vary greatly at different times. It is necessary, however, that the volume of current traversing anyindividual local circuit when closed must be always practically the same, and this renders it essential to introduce a self-regulating principle into the system.

I will now proceed to explain the manner in which this is effected. The internal resistance of the coil of the armature A between the terminals and a should be made as small as possible, having due regard to its capacity at a normal speed of revolution to maintain the required difference of potential between said terminals. The office of the exciting or field coil F F is to maintain the magnetic condition of the field-magnets, which is effected by diverting thereto a portion of the current proceeding from the armature A. The length of the conductor composing the field-coil is much greater than that of the armature-coil and the wire much thinner, so that its total resistance is very much greater. It may with advantage be as much as one thousand times as great as that of the armature. The resistance presented by the external or working circuit 1? N depends, principally, upon two things, first, the resistance of the individual sounders or other electro-magnetic receivinginstruments S S, which are included in the several local circuits, and, second, upon the number of these through which the circuit is' t-ion'is observed that the apparatus can be rendered self'regulating.

In order to illustrate more clearly the manner in which the automatic regulation takesplace, let it be assumed that the leads P N are united by one hundredlocal circuits, each having a resistance, including its sounder S, of filty ohms. The minimum resistance of the external circuit, P N ,will' obviously be when all theselocal-circuits aresi-multaneously closed,in which case the joint resistance will be 0.50, or half an ohm. Let us assume the resistance of the armature-coil to be 0.01, or one-hundredth ofan-ohm,and that of the field coils twenty-five ohms, and let it be assumed that under these conditions the dynamo electric machine is capable of maintaining asufficient potential to supply all the local circuits with a proper current. If, now, we suppose all the local circuits, except one, to be interrupted by the action of the relays, the resistance of the circuit P N is increased to fifty ohms. The absolute quantity of current generated and flowing from the armature by reason of this increase in the resistance is greatly diminished; but the proportion of this current from the armature which traverses the field coil is at the same time greatly increased, so that there is little or no change in the actual strength or magnetizing effect of the current traversing the field-coil; hence the potentialor electro-motive force of the system, which depends solely upon two factors-viz., the strength of the magnetic field, and the speed of the armatureremains practically unchanged, and therefore the potential, when only one local circuit is closed is practically the same as when the whole number are closed. These proportions may be secured in practice by making the coils of the sounders of a large number of convolutions of very thin wire, and thereby giving to them a resistance many times greater than those in the ordinary use, and by employing a current of correspondingly higher potential.

The best results in automatic regulation are found to be attained in practice when the ratio of the armature-resistance to the minimum resistance of the external circuit is the same as that of the latter to the resistance of the field.

I claim as my invention- 1. The combination of a dynamo electric generator'having an armature coil or coils of low resistance and a field or exciting coil or coils of comparatively high resistance placed in multiple arc with each other, with agroup of electro magnetic instruments placed in multiple arc with the said field and armature coils, and having a minimum joint resistance which is a mean proportion between the re sistance of the armature-coils and that of the field-coils, as set forth.

2. The combination of a dynamo-electric generator having an armature coil or coils of low resistance and a field or exciting coil or coils of comparatively high resistance placed in multiple arc with each other, with agroup of electromagneticinstruments placed in multiple arc with the said field and armature coils, and having a minimumjoint resistance which is a mean proportion between the resistance of the armature-coils and that of the field-coils, and'a series of circuit-breakers, one for each electro-magnetic instrument, as set forth.

3. The combination of a dynamo -electric generator having an armature coil or coils of low resistance and a field or exciting coil of comparatively high resistance placed in multiple arc with each other, with a group of electro-magnetic instruments, each provided with a circuit-breaker and placed in multiple arc with the said field and armature coils, and having a minimum joint resistance which is a mean proportion between the resistance of the armature-coils and that of. the fieldcoils, a series of circuit-breakers, one for each electro magnetic instrument, and an independent electro-magnet for actuating each of said circuit-breakers, as set forth.

In testimony whereof I have hereunto subscribed my name this 9th day of March, A. D. 1885.

- FRANK L. POPE.

Witnesses:

DANL. W. EDGEOOMB, CHARLES A. TERRY. 

